The microstructure and the electrical conductivity of MgO-doped Cr2O3 were investigated as a function of oxygen partial presure, temperature, and MgO content. The grain size was estimated about 1.0$mu extrm{m}$. The solubility limit is increased with oxygen partial pressure. Above the solubility limit of MgO in Cr2O3, the spinel phase(MgCr2O4) is formed by the reaction of MgO and Cr2O3. The electrical conductivity of MgO-doped Cr2O3 within the solubility limit is increased with MgO content. Above the solubility limit, however, it is decreased with increasing MgO content because of the formation of the spinel phase.